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Optimize inner-loop in JSON.stringify.

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R=verwaest@chromium.org
BUG=

Review URL: https://chromiumcodereview.appspot.com/11234031

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12798 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This commit is contained in:
yangguo@chromium.org 2012-10-23 09:05:56 +00:00
parent 5677ee6565
commit 748f8bf7e1
1 changed files with 67 additions and 44 deletions
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111
src/json-stringifier.h
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@ -58,15 +58,9 @@ class BasicJsonStringifier BASE_EMBEDDED {
template <bool is_ascii, typename Char>
INLINE(void Append_(Char c));
template <bool is_ascii, typename Char>
INLINE(void AppendUnchecked_(Char c));
template <bool is_ascii, typename Char>
INLINE(void Append_(const Char* chars));
template <bool is_ascii, typename Char>
INLINE(void AppendUnchecked_(const Char* chars));
INLINE(void Append(char c)) {
if (is_ascii_) {
Append_<true>(c);
@ -123,10 +117,18 @@ class BasicJsonStringifier BASE_EMBEDDED {
void SerializeString(Handle<String> object);
template <typename SrcChar, typename DestChar>
INLINE(void SerializeStringUnchecked_(const SrcChar* src,
DestChar* dest,
int length));
template <bool is_ascii, typename Char>
INLINE(void SerializeString_(Vector<const Char> vector,
Handle<String> string));
template <typename Char>
INLINE(bool DoNotEscape(Char c));
template <typename Char>
INLINE(Vector<const Char> GetCharVector(Handle<String> string));
@ -152,12 +154,14 @@ class BasicJsonStringifier BASE_EMBEDDED {
int part_length_;
bool is_ascii_;
static const int kJsonQuotesCharactersPerEntry = 8;
static const char* const JsonQuotes;
static const int kJsonEscapeTableEntrySize = 8;
static const char* const JsonEscapeTable;
};
const char* const BasicJsonStringifier::JsonQuotes =
// Translation table to escape ASCII characters.
// Table entries start at a multiple of 8 and are null-terminated.
const char* const BasicJsonStringifier::JsonEscapeTable =
"\\u0000\0 \\u0001\0 \\u0002\0 \\u0003\0 "
"\\u0004\0 \\u0005\0 \\u0006\0 \\u0007\0 "
"\\b\0 \\t\0 \\n\0 \\u000b\0 "
@ -235,31 +239,12 @@ void BasicJsonStringifier::Append_(Char c) {
}
template <bool is_ascii, typename Char>
void BasicJsonStringifier::AppendUnchecked_(Char c) {
if (is_ascii) {
SeqAsciiString::cast(*current_part_)->SeqAsciiStringSet(
current_index_++, c);
} else {
SeqTwoByteString::cast(*current_part_)->SeqTwoByteStringSet(
current_index_++, c);
}
ASSERT(current_index_ < part_length_);
}
template <bool is_ascii, typename Char>
void BasicJsonStringifier::Append_(const Char* chars) {
for ( ; *chars != '\0'; chars++) Append_<is_ascii, Char>(*chars);
}
template <bool is_ascii, typename Char>
void BasicJsonStringifier::AppendUnchecked_(const Char* chars) {
for ( ; *chars != '\0'; chars++) AppendUnchecked_<is_ascii, Char>(*chars);
}
Handle<Object> BasicJsonStringifier::GetProperty(Handle<JSObject> object,
Handle<String> key) {
LookupResult lookup(isolate_);
@ -579,34 +564,60 @@ void BasicJsonStringifier::ChangeEncoding() {
}
template <typename SrcChar, typename DestChar>
void BasicJsonStringifier::SerializeStringUnchecked_(const SrcChar* src,
DestChar* dest,
int length) {
dest += current_index_;
DestChar* dest_start = dest;
*(dest++) = '"';
for (int i = 0; i < length; i++) {
SrcChar c = src[i];
if (DoNotEscape(c)) {
*(dest++) = c;
} else {
const char* chars = &JsonEscapeTable[c * kJsonEscapeTableEntrySize];
while (*chars != '\0') *(dest++) = *(chars++);
}
}
*(dest++) = '"';
current_index_ += dest - dest_start;
}
template <bool is_ascii, typename Char>
void BasicJsonStringifier::SerializeString_(Vector<const Char> vector,
Handle<String> string) {
int length = vector.length();
if (current_index_ + (length << 3) < (part_length_ - 2)) {
AssertNoAllocation no_allocation_scope;
AppendUnchecked_<is_ascii, char>('"');
for (int i = 0; i < length; i++) {
Char c = vector[i];
if ((c >= '#' && c <= '~' && c != '\\') ||
(!is_ascii && ((c & 0xFF80) != 0))) {
AppendUnchecked_<is_ascii, Char>(c);
} else {
AppendUnchecked_<is_ascii, char>(
&JsonQuotes[c * kJsonQuotesCharactersPerEntry]);
}
// We make a rough estimate to find out if the current string can be
// serialized without allocating a new string part. The worst case length of
// an escaped character is 6. Shifting left by 3 is a more pessimistic
// estimate than multiplying by 6, but faster to calculate.
static const int kEnclosingQuotesLength = 2;
if (current_index_ + (length << 3) + kEnclosingQuotesLength < part_length_) {
if (is_ascii) {
SerializeStringUnchecked_(
vector.start(),
SeqAsciiString::cast(*current_part_)->GetChars(),
length);
} else {
SerializeStringUnchecked_(
vector.start(),
SeqTwoByteString::cast(*current_part_)->GetChars(),
length);
}
AppendUnchecked_<is_ascii, char>('"');
} else {
Append_<is_ascii, char>('"');
String* string_location = *string;
for (int i = 0; i < length; i++) {
Char c = vector[i];
if ((c >= '#' && c <= '~' && c != '\\') ||
(!is_ascii && ((c & 0xFF80) != 0))) {
if (DoNotEscape(c)) {
Append_<is_ascii, Char>(c);
} else {
Append_<is_ascii, char>(&JsonQuotes[c * kJsonQuotesCharactersPerEntry]);
Append_<is_ascii, char>(
&JsonEscapeTable[c * kJsonEscapeTableEntrySize]);
}
// If GC moved the string, we need to refresh the vector.
if (*string != string_location) {
@ -619,6 +630,18 @@ void BasicJsonStringifier::SerializeString_(Vector<const Char> vector,
}
template <>
bool BasicJsonStringifier::DoNotEscape(char c) {
return c >= '#' && c <= '~' && c != '\\';
}
template <>
bool BasicJsonStringifier::DoNotEscape(uc16 c) {
return (c >= 0x80) || (c >= '#' && c <= '~' && c != '\\');
}
template <>
Vector<const char> BasicJsonStringifier::GetCharVector(Handle<String> string) {
String::FlatContent flat = string->GetFlatContent();